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I have been driving this car for some time now (Ford Focus ZX4 2005). I have been seeing 25 - 27 MPG every time I fill up. I drive a little (10 min) in city and then the rest of my destination on the highway (20 min). I have a OBDII reader and Torque Pro and I gathered Bank 1 Sensor 1 and 2 as well as Short and Long Term Fuel Trim. NOT sure if the program is under-sampling.

Section of the read from my car showing WOT segment

So looking from the graph above... can you guys make assumptions on weather or not my O2 sensor are functioning or if you can see something else let me know.

I have been watching lots of videos on O2 sensors as well fuel trim banks stuff. BUT I am no position to make guesses on my car. BUT if there is something wrong and can improve my MPG I will be happy :D. If not, I will end my search and live with it. Thanks in advance.

  • From the data shown in the bar graph, I think you could easily assume that the O2s are working correctly. What you are looking for is the upstream O2 to be all over the place (lots of movement), with the downstream O2 staying fairly steady. That's what I believe I'm seeing here. – Pᴀᴜʟsᴛᴇʀ2 Mar 18 '15 at 20:35
  • Engine size and automatic or manual transmission? – Move More Comments Link To Top Mar 18 '15 at 21:10
  • automatic and 2.0L, Sedan – Dave P Mar 18 '15 at 21:20
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Based on fueleconomy.gov your are getting a little better than what's expected.

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Comparing the less accurate old rating system to the new, it's still not as high as you were expecting, but it was higher.

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Compare Old and New MPG Estimates

The manual transmission with the 2.0 gets the best mileage that year

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If you look up mpg on some sites it just give you the highest mpg listed for the vehicle without taking into account the engine, transmission, or other options that effect fuel mileage. That may be why you were expecting high mpg.

To address you other question, the O2 sensor appear to be operating normally.

If you want to get better gas mileage, there are plenty of things you can do, Here are a few that come to mind.

  • Don't carry anything in the car you don't need. More weight means less MPG
  • Accelerate slowly
  • Let off the accelerator sooner when you are coming to a stop.
  • Make sure you tire pressures are not low. Some people even run them 2 - 5 psi higher than recommended to improve mileage. (Side note never go over the max pressure listed on the tire, also may affect tire wear, handling, and traction)
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  • Huh... i was told / shown that it does like about 34mpg range on the hwy. Ok i feel much better now lol, been digging for an answer for something that doesn't exists. I thought i saw it on MSN cars or something like that. I'v must of had the wrong year when i was first looking into it and locked myself to that number. – Dave P Mar 19 '15 at 0:55
  • @DaveP You may have seen the pre-2008 ratings for that car. The old system of testing for mpg by the manufactures was not even close to real world mileage the consumer would see. The standard was changed in 2008. See 2008 Ratings Changes for more info – Move More Comments Link To Top Mar 19 '15 at 2:57
  • @DaveP I have also edited my answer to include more info on the different ratings. – Move More Comments Link To Top Mar 19 '15 at 3:10

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